Cracking of hydrocarbon oils



IML 2, 194@ P. c. KEITH, JR., ET A1. 2,185,200

CRACKING OF HYDROCARBON OILS Original Filed Feb. ll, 1937 2 Sheets-Sheetl ORS ATTORNEY Nm. MQ

M1- 2, 1940- P. c. KEITH. JR., ET A1. 2,185,200

CRACKING OF HYDROCRBON OILS Original Filed Feb. ll, 1937 2 Sheets-Sheet2 c or non i z Percival G. heith, Jr., Peapack, N. i., and Joseph h,herts, iilossmoor, Ml., assignors of onehali' to Standard @il Company,Chicago, lill., a coration of llndana, and one-half to Gasoline ProductsUompany, line.,

.liersey mty,

N. li., a cor-ation of Delaware @i mi application February 1l., 1937,Serial 125,204. Divided and this application liliecemher 2t, 1938,Serial No. 246,774

i application is a division of our pending iiication, Serial No.125,204, filed February 11,

This invention relates to processes for the treatment of hydrocarbon oiland pertains more particularly to processes adapted for the productionof gasoline or other light distillate from heavy oil such as crudepetroleum, partially reduced crude or the like.

it is an object of our invention to provide a combination cracking unitor process wherein the crude petroleum is 'subjected to a distillingoperation to separate virgin gasoline, heavy naphtha, kerosene, gas oiland reduced crude oil, and to provide for the separate treatment ofthese several iractions.

A feature oi our invention resides in the oncethrough cracking of theheavy reduced crude and the introduction thereof into a vapor separatingand fractionating system, from Whicha heavy gas oil condensate isWithdrawn: separately cracked, and returned to the evaporating andfractionating system, this latter operation being conducted on arecycling basis.

.another feature resides in the removal of the kerosene fraction fromthe process and the separate cracking or reforming of a mixture of thevirgin heavy naphtha and virgin gas oil and the passage of the resultingcracked products to an evaporating and fractionating system.

i further feature resides in a particular method of connecting togetherthe two separate evaporating and iractionating systems whereby economyof operation is attained.

The invention contemplates a combination cracking process in which-acrude petroleum stock is subjected to fractionation to form a residueand a lighter fraction, in which the residue is passed to a primarycracking or viscositybreaking Zone wherein the residue is subjected tocracking temperature under conditions to eect the formation of a highyield of gas oil constituents, adapted for conversion into gasoline, theresultant viscosity-broken products separated into vapors and residueand the vapors fractionated to form a heavy reflux condensate and alighter fraction comprising such intermediate constituents, in which theheavy reflux condensate is pressed to a secondary viscosity-breaking orheavy gas oil cracking zone wherein the heavy condensate is subjectedto'cracking temperature under conditions to eect the formation of anadditional yield of gas oil constituents adapted ior conversion intogasoline, the resultant cracked products separated into vapors and resi,

(ci. isc-i9) due and the separated vapors fractionated together with thevapors separated from the cracked products of the primaryviscosity-breaking operation so as to combine gas oil constituentsformed in the two cracking or viscosityt breaking operations, in whichsuch lighter fractions from the crude fractionating operation and fromthe cracking or viscosity-breaking operations mentioned are combined andthe mixture subjected to cracking in a third cracking zone ll@ underhigh cracking temperature and under conditions of high' cracking perpass'to eect conversion into gasoline of high anti-knock quality and thecracked products separately fractionated to recover the desired gasolineproduct.

In accordance with the invention the cracked products from the third orhigh cracking per pass. cracking zone are separated into vapors andresidue and the vapors fractionated to form a reflux condensate which issubjected to cracking in a recycling cracking zone while the admixedfractions from the crude fractionating step and from theviscosity-breaking operations are subjected to cracking in a single-passcracking zone.

The invention further contemplates the vacuurn-flashing of residualmaterial separated out from the viscosity-broken products from theviscosity-breakng operations to form heavy residue and vacuum-flasheddistillate, and the combining of vacuum-flashed distillate constituentswith the heavy reflux condensate passing to the secondaryviscosity-breaking or heavy gas oil cracking zone. In accordance withthe invention the vacuum-flashed distillate is introduced into thefractionating zone in which the vapors from both of theviscosity-breaking zones are fractionated so that any portion of thevacnum-flashed distillate remaining unvaporized after contact with thevapors undergoing fractionation therein Will be charged to the secondaryviscosity-breaking or heavy gas oil cracking zone with the heavy refluxcondensate being directed thereto.

In accordance with our invention the fresh heavy charging oil such ascrude oil, partially reduced crude or the like, is preheated by anysuitable method such as indirect heat exchange or direct heating in aiired coil, or both, and then introduced into a crude flash tower, fromwhich a gasoline fraction, heavy naphtha fraction,

vkerosene fraction, gas oil fraction and reduced crude are withdrawn.The reduced crude is passed once through a cracking heater wherein it israised to a cracking temperature and subjected to conversion and thecracked oil ls then passed to an evaporating zone, the vapors from whichare subjected to fractional condensation with the resulting formation ofa heavy gas oil condensate and an overhead light distillate coprisinggasoline and light gas oil, but which may comprise substantially onlygasoline. The heavy condensate is removed, passed through a separatecracking zone and returned to the evaporating zone while the overheadlight distillate is combined with the virgin heavy naphtha and gas oiland the mixture is passed through a third cracking zone wherein crackingand reformation occurs, the products of conversion then being introducedinto a high pressure evaporator wherein separation of vapors fromresidue takes place. The separated vapors are subjected to fractionationin a separate relatively high pressure fractionator to form a refluxcondensate which is directed to a recycling cracking coil, lthe crackedproducts from which are discharged into the high pressure evaporator.'I'he fractionated vapors from the high pressure fractionator areremoved and condensed as a desired product.

Liquid residue from the high-pressure evaporator is preferably flashedin a flash tower under reduced pressure, the ilashed vapors beingconducted to the low-pressure fractionating system. At the same timeresidue from the low-pressure evaporator is preferably Withdrawn andflashed in a separate flash drum under vacuum, the overhead distillateobtained being returned to the lowpressure evaporating and fractionatingsystem, most suitably in such manner that unvaporized portions thereofare passed through the second cracking zone with the heavy condensate.

Where different types of crude oil are charged different quantities ofheat must be supplied thereto for effecting distillation and, toaccomplish this most eillciently, an auxiliary furnace is providedthrough which the crude charging oil may be passed in one directionprior to introduction into the crude ilash tower. Provision is also madefor passing recycle stock from the highpressure fractionator in theopposite direction through this auxiliary furnace when that furnace isnot being used for preheating crude oil.

The above-mentioned and further objects and advantages of .our inventionand the manner of attaining them will be more fully set forth in thefollowing description taken in conjunction with the accompanyingdrawings.

Figure 1 illustrates diagrammatically in side elevation apparatusadapted to carry out the process of the invention.

Figure 2 is a simplified flow diagram of the invention.

Referring more particularly to the drawings, heavy charging .oil such ascrude oil, partially reduced crude or the like is introduced throughline I and forced by pump 2 into crude flash tower 3, after havingpassed through suitable preheating means such as heat exchangers 4 and 5wherein the oil is raised to a distillation temperature, and by-passline 6. Alternatively the oil may travel through heating coil 1 offurnace 8 to pick up suillcient heat for distillation purposes, valves9, I0, and II providing the necessary control.

In tower 3 the crude oil is fractionally distilled to form an overheaddistillate of light naphtha, i. e., the light ends of gasoline, which isremoved via vapor line I2 and condenser I3 and collected in receiver I4,and naphtha, kerosene, and gas oil condensates, which are collected ontrap-out trays I5, I6, and I1 respectively, and

reduced crude which is collected at the base of the tower. These severalcondensates are conducted through valved lines I8, I9, and 20 intostrippers 2l, 22 and 23 respectively, wherein they are stripped oflighter ends by aid of steam or gas introduced through connections |50.The kerosene is preferably withdrawn from the process through valvedline 24 as a desired product while the heavy naphtha comprising heavyends of gasoline, and gas oil condensate are introduced into accumulator25 by way of valved connections 26 and 21. The latter connectionincludes heat exchanger 28 which may be by-passed by means of valvedline 29. Kerosene when not withdrawn from the process may likewise bepassed to accumulator 25 through valved pipe I5I. Vapors from theseveral strippers and from the accumulator are returned to the tower 3by means of vapor pipes 30, 3|, 32 and 33.

Reduced crude is withdrawn from the base of tower 3 through pipe 34 andforced by pump 35 through heating coil 36 located in furnace 31, whereinit is subjected to mild cracking conditions to effectviscosity-breaking. The cracked products pass through transfer line 38having control valve 39, into the evaporator portion 40 of combinationtower 4I, wherein vapors separate from liquid residue. The vapors travelupwardly through the tower around baille plates .or other contactelements 42, then through fractionator section 43 of the tower havingbubble trays or other fractionating elements 44. The fractionated vaporsof desired boiling characteristics, e. g., gasoline, pass through vaporpipe 45, are cooled in heat exchanger 46A and 41, and condensed incondenser 48, and the distillate is collected in receiver 49 which isequipped with the usual gas vent line 50 and liquid withdrawal line 5I.

Heavy gas oil condensate is collected on trapout tray 52 from which itis withdrawn through conduit 53 and forced by pump 54 through heatingcoil 55 in furnace 31. In this coil the oil is raised to a moderatecracking temperature, preferably somewhat higher than that to which theoil is raised in coil 36, and is subjected to a moderate degree ofconversion. The resulting cracked products pass through transfer line 56having control valve 51 into the evaporator section 40 of tower 4 I.

Liquid residue is directed from the base of tower 4I through pipe 58having reducing valve 59, into vacuum flash tower 60 wherein lighterconstituents thereof are distilled by their contained heat, leaving aheavy tar residue which is drawn o from the process through valved line6I having pump 62, for use alone or in mixture with other tar ordistillate from the process. The vacum flash tower may operate under anabsolute pressure of, for example, about '70 millimeters of mercury. Theflashed vapors are removed through vapor pipe 63, heat exchanger 63A andcondenser 64 and the distillate is collected in receiver 65, from whichpart is returned via line 66 under pressure of pump 61, to the flashtower as a reiluxing medium while the remainder is conducted by conduit68 into fractionator section 43 through branch connection 69 and heatexchanger 63A or through branch connections 'I0 and 1I into evaporatorsection 40. Each of these connections is furnished with a control valveas shown. Gas oil may be circulated from tray 52 through conduit 12having pump 13 and cooler 14 into any or all of the branch connectionsmentioned for use as a refluxing or cooling medium. Reference numeral 46indicates an exhausting aieaaoo device such as a. pump or barometriccondenser for producing a vacuum in the ash tower.

'I'he mixture of virgin heavy naphtha and gas oil is removed fromaccumulator 25 by way of pipe 15 and is forced by pump 16 throughheating coil 11 located in furnace 96 wherein it is raised to a highcracking temperaturesufiicient to form high anti-knockgasolinefractions, and the cracked products are conducted into the lowerportion of evaporator 18 through pipe 19 having control valve 80. In theevaporator vapors separate from liquid residue, the latter being drawnoff through pipe 8| having reducing valve 82, into flash drum 83 whereinlighter constituents are vaporized by their contained heat leaving ashedliquid residue which is withdrawn from the procprocess.

Vthe radiant section llll.

ess via line 84 as fuel oil. If desired this flashed residue may beblended with tar removed from vacuum ash tower 60 or with bottoms fromtower 81 or both. The flashed vapors flow .through vapor pipe 85 intofractionator section 43 Vapors from evaporator 18 travel through vaporline 86 into fractionator 81 and are therein fractionated in the usualway to give overhead vapors of the desired boiling characteristics, e.g.. gasoline, which are removed by way of vapor pipe 88 and condensed incondenser 89, the distillate being collected in receiver 99 as a productof the in the base of the fractionator, is withdrawn by way of line 9|and forced by pump 92 through heating coil 93 in furnace 96 and istherein raised to an active cracking temperature which may be somewhatless than that attained by the oil traversing coil 11 but in excess ofthat to which the reduced crude and heavy gas oil condensate are raisedin their respective heating coils. The cracked products so derived areconducted through transfer line 98 having control valve 95 into the baseof evaporator 18.

Alternatively part or all of the reux condensate from the base offractionator 81 may be forced through pipe 91 and heating coil 1 offurnace 8 when this heating coil is not being used for heating freshcharging oil. In this heating coil the oil is raised to a crackingtemperature such as that attained in the coil 93 and is then conductedthrough transfer line 98 having control valve 99 into the evaporatortower 18. In this manner of operation the gas oil passes through theheating coil 1 by entering the convection section |08 of the coil andleaving through When this coil is used for preheating crude oil the flowis in the opposite direction, the crude oil entering the radiant section185| and leaving through the convection section |89. Valves |82 and |03are provided for controlling the flow of gas oil conducted from thetower 81 to the heating furnaces.

Cooling at the top of the fractionator tower 81 is provided bywithdrawing a side stream of reflux condensate through line |08 andpassing it through heat exchanger and auxiliary cooler |05 into the topof the tower, the necessary pressure being provided by pump |85. Coolingfor the top of fractionator section 83 of combination tower 8| iseffected by pumping back to the top of the tower through pipe |01 underpressure generated by pump |88, a portion of the gasoline i control.

collected in receiver 89. Another portion of this same gasolinedistillate may be directed through connection |09 into the top of fueloil flash tower 38, valves H and furnishing the necessary Cooling forthe top of crude ash tower Clean gas oil reux condensate collects Y 3 isprovided in a like manner, a portion of the gasoline collected inreceiver i4 being forced through pipe H2 and pump H3 into the top ofthat tower, the necessary control being brought about through valve H4.Reflux condensate is withdrawn from trap-out tray H5 in tower 81 anddirected by pressure of pump H1 through conduit H6 and heat exchanger 5in indirect heat exchange relation with the crude oil charging stock,thence through auxiliary cooler H9 and pipe to an intermediate point inthe tower 81. A line I2| is provided to return a portion of this cooledreux condensate to different levels in the evaporator tower 18 by way ofvalved pipes |22 and |23. A by-pass control line |28 is arranged acrossthe terminals of auxiliary cooling coil H9 for control purposes. Aconnection is furnished for leading oil to the base of the fractionatorthrough valved pipe |26 and to the transfer lines 19 and 98 by way Eofvalved terminal lines |21 and |28. Pump |29 gives the necessary presSure. By means of this line last-mentioned uxing oil is injected intothe transfer line to prevent coking diiculties. Surplus oil returns tofractionator 81 through the pipe |26.

Distillate collected in receiver |39 may be diverted from the processthrough draw-ofi line 5|, but preferably this distillate is passedthrough pipe |3|, heat exchanger 28, pipe |32, heat exchanger 81, andpipe |33, into an intermediate level in fractionator tower 81. By-passvalve H8 is provided so that part or all of this distillate may bedirected to conduit 15 for passage with the Virgin stock through heatingcoil 11. In this case the distillate would desirably be mainly gasolinewhich itis desired to reform. Valved pipe |5| is provided to by-passheat exchanger 28.

By returning distillate from the receiver 49 to either the fractionator81 or the evaporator 18 or to both the fractionator 81 and evaporator18. refractionation thereof takes place with the desirably lightconstituents passing 01T overhead through vapor line 88 to be collectedwith the nal desired gasoline distillate in receiver 90. Sincerefractionation takes place the end point of the distillate collected inreceiver 49 need not be exactly that of the final desired product but itmay be somewhat heavier including even light gas oil. In most instancesit will be found desirable to pass the light gas oil into the receiver49 so that it can be introduced into the fractionator tower 81 and findits way through connection 9| to heating coil 93 for further cracking atfairly high cracking temperatures,

Reference numeral |35 indicates a reduced pressure stripper tower intowhich an intermediate reflux condensate cut in the boiling range oflight gas oil or furnace or tractor oil, for example, is directed by wayof draw-off line |36 which is connected to a trap-out tray |31 in thefractionator 81. 'I'his oil, after undergoing stripping in the tower|35, is withdrawn from the process as a desired product, e. g., furnaceoil, through valved draw-ofi line |38 while the overhead vapors rom thisstripper tower travel through pipe |39 into vapor line 45 for passagethrough condenser 88. A refluxmg line for passing distillate from pipe|33 to the top of the stripper tower |35 is referred to by numeral |40.

In actual operation the temperature of the oil leaving the, initialviscosity-breaking coil 36 is preferably in the neighborhood of 870900F. and the pressure desirably being about 150-200 pounds per squareinch. The temperature may, however, range fromA 850 to 950 F., more orless, and the pressure may be higher or lower than that indicated aspreferable, extending, for example, from 75 pounds to 400 pounds persquareinch, more or less. The heavy gas oil upon emerging from heatingcoil 55 preferably has a temperature of about 950 F., the pressure beingdesirably about 400 pounds per -square inch. These values are preferredbut the temperature may vary considerably ranging, for example, from 900to 1000 F., and the pressure ranging from a few pounds per square inchto as high as 1000 pounds per square inch or more.

The mixture of virgin heavy naphtha and gas oil passing through theheating coil 'Il is raised to a higher cracking temperature of, forexample, about 1000 F.1020 F. under a pressure of, for example, about750 pounds per square inch although the temperature may range from 950to 1150 F. and the pressure may also vary considerably, for example from200, pounds to 1000 pounds per square inch. The reflux condensate fromthe base of fractionating column 81 is heated in the coil 93 or in thecoil 1, if that be used, under substantially the saine conditions oftemperature and pressure as mentioned for oil leaving coil 17, althougha somewhat higher temperature and lower pressure may be used in someinstances. The pressure maintained in the two evaporating zones 'I8 and40 will depend upon the pressures used in the heating coils, necessarilybeing lower than the outlet pressure of any heating coil dischargingthereinto. However, the pressure in evaporator 'I8 will be higher thanthat held in evaporator section 40, the pressure in the former being,for example, about D-300 pounds per square inch and that in the latterabout 50 pounds per square inch, more or less.

With this type of operation a suitable boiling range for the kerosenefraction removed from the crude ash tower and diverted from the processis about 450 to 550 F. This is merely illustrative as the boiling ran-gemay be somewhat higher or lower. The heavy naphtha and .the gas oilwhich are mixed in accumulator for cracking together in coil 'I'I mayhave boiling ranges of from 250 to 450 F., and 550 to 750 F.,respectively, for example. The boiling range of the naphtha will dependupon the anti-knock value desired for the final gasoline distillate, the

-higher the anti-knock value necessary the greater the quantity ofnaphtha which must be reformed and accordingly the lower the initialboiling point of the naphtha passed through coil Tl. The conversion toproducts in the gasoline boiling range per pass in the heating coils 36,55, 11, and 93, may be about 10%, 15%, 60% and 20% respectively. Butthese values are merely illustrative and may be varied to suit differentcharging stocks and different desired products. Obviously the lighterand cleaner the stock the higher the rate of conversion may be.Referring to the coil 'l1 high conversions per pass will follow fromhigh initial gasoline content. Reaction chambers may be used with any orall of the cracking coils to provide for additional cracking.

In an alternative method of handling a crude oil charging stock, thecrude charge introduced by pump 2, after preheating in heat exchangers,such as 4 and 5, instead of being passed directly to the crude flashtower 3, is introduced into a pre-flash drum for the release of lightvapors which are passed into the lower part of the crude flash tower 3,and the residue from the pre-flash drum is passed through heating coil 1and the heated crude directed through line 6 into the flash tower 3.

While we have described a particular embodiment of our invention forpurposes of illustration, it should be understood that variousmodiiications and adaptations thereof which will be obvious to oneskilled in the art, may be made within the spirit of the invention asset forth in the appended claims.

We claim:

1. In the cracking of hydrocarbon oils the process that comprisessubjecting crude petroleum in a primary fractionating zone tofractionation to form a residue and a lighter fraction, passing saidresidue to a primary viscosity-breaking zone wherein the residue issubjected to cracking temperature under conditions to effect theformation of a high yield of gas oil constituents adapted for conversioninto gasoline, directing the viscosity-broken products into a separateevaporating zone wherein separation of vapors from residue takes place,passing the separated vapors into a separate fractionating zone andsubjecting the vapors therein to fractionation to form a heavy refluxcondensate and a lighter fraction, passing resultant heavy refluxcondensate to a secondary viscosity-breaking zone wherein the heavycondensate is subjected to cracking temperature under conditions toeffect the formation of a high yield of gas oil constituents adapted forconversion into gasoline, separating the latter viscosity-brokenproducts into vapors and residue and passing the separated vapors intosaid separate fractionating zone, combining said lighter fractionsobtained from the viscosity-broken products and from the crude petroleumfractionation and subjecting the combined fractions to cracking in aseparate cracking zone under high cracking temperature and underconditions of high cracking per pass to effect conversion to gasoline ofhigh antiknock quality and directing the resultant products of thelatter cracking into a separate fractionating zone to recover thedesired gasoline product.

2. In the cracking of hydrocarbon oils the process that comprisessubjecting crude petroleum in a primary fractionating zone tofractionation to form a residue and a lighter fraction, passing saidresidue to a primary Viscosity-breaking zone wherein the residue issubjected to cracking temperature under conditions to effect theformation of a high yield of gas oil constituents adapted for conversioninto gasoline, directing the viscositybroken products into a separateevaporating zone wherein separation of vapors from residue takes place,passing the separated vapors into a separate fractionating zone andsubjecting the vapors therein to fractionation to form a heavy reuxcondensate and a lighter condensate comprising such gas oilconstituents, passing resultant heavy reux condensate to a secondaryviscositybreaking zone wherein the heavy condensate is subjected tocracking temperature under conditions to effect the formation of a highyield of gas oil constituents adapted for conversion into gasoline,separating the latter viscosity-broken products into vapors and residueand passing the separated vapors into said separate fractionating zone,combining said lighter fractions obtained from the viscosity-brokenproducts and from the crude petroleum fractionation and subjecting thecombined fractions to cracking in a separate cracking zone under highcracking temperature lili dit

and under conditions of high cracking per pass to eect conversion togasoline of high anti-knock quality, directing the resultant products ofthe latter cracking into another evaporating zone wherein separation ofvapors from residue takes place, passing the separated vapors into aseparate fractionating zone wherein the vapors are fractionated to forma reiiux condensate and a nal distillate product, passing resultantreflux condensate to a fourth cracking zone wherein it is subjected tocracking temperature to elfect conversion into gasoline constituents anddirecting the resultant products of conversion into said latterseparating zone.

3. In the cracking of hydrocarbon oils the process that comprisesprimarily subjecting crude petroleum to a stripping operation toseparate it into vapors and residue and fr actionating the vapors toform a condensate, passing said residue to a primary viscosity-breakingzone wherein the residue is subjected to cracking temperature underconditions to effect the formation of a high yield of gas oilconstituents adapted for conversion into gasoline, directing theviscosity-broken products into a separate evaporating zone whereinseparation of vapors from residue takes place, passing the separatedvapors into a separate fractionating zone and subjecting the vaporstherein to fractionation to form a heavy reux condensate and a lightercondensate comprising such gas oil constituents, passing resultant heavyreux condensate to a secondary viscosity-breaking zone wherein the heavycondensate is subjected to cracking temperature under conditions toeffect the formation of a high yield of gas oil constituents adapted forconversion into gasoline, directing the latter viscosity-broken productsinto said separate evaporating zone, combining said lighter condensateobtained from the viscositybroken products with said condensate obtainedfrom the stripping of the crude petroleum and subjecting the combinedcondensates to cracking in a separate cracking zone under hightemperature and conditions of high cracking per pass to eect conversioninto gasoline of high anti-knock quality, directing the resultantproducts of the latter cracking into another evaporating zone whereinseparation of vapors from residue takes place, passing the separatedvapors into a separate fractionating zone wherein the vapors arefractionated to form a reux condensate and a nal distillate product,passing resultant reflux condensate to a fourth cracking zone wherein itis subjected to cracking temperature to effect conversion into gasolineconstituents and directing the resultant products of conversion intosaid latter separating zone. p

i. In the cracking of hydrocarbon oils the process thatcomprises-subjecting crude petroleum in a. primary fractionating zone tofractionation to form a residue and a lighter fraction, passing saidresidue to a primary viscosity-breaking zone wherein the residue issubjected to cracking temperature under conditions to eifect theformation of a high yield of gas oil constituents adapted for conversioninto gasoline, directing the'viscositybroken products into a separateevaporating zone wherein separation of vapors from residue takes place,passing the separated vapors into a separate fractionating zone andsubjecting the vapors therein to fractionation to form a heavy reuxcondensate and a lighter condensate comprising such gas oilconstituents, passing resultant heavy reflux condensate to a secondaryviscositybreaking zone wherein the heavy condensate is subjected tocracking temperature under conditions to effect the formation of a highyield of gas oil constituents adapted for conversion into gasoline,directing the latter viscosity-broken products into said separateevaporating zone, withdrawing residue from the latter evaporating zoneand subjecting it to vacuum distillation in a flashing zone held undersub-atmospheric pressure to form heavy residue and vacuum-'flasheddistillate and combining resultant Vacuum-flashed distillateconstituents with the heavy reiiux condensate passing to the secondaryviscosity-breaking zone, combining said lighter fractions obtained fromthe viscosity-broken products and from the crude petroleum fractionationand subjecting the combined fractions to cracking in a separate crackingzone under high cracking temperature and under conditions of highcracking per pass to effect conversion to gasoline of high anti-knockquality and directing the resultant products of the latter cracking intoa separate fractionating zone to recover the desired gasoline product.

5. In the cracking of hydrocarbon oils the process that comprisessubjecting crude petroleum in a primary fractionating zone tofractionation to form a residue and a lighter fraction, passing saidresidue to a primary Viscosity-breaking zone wherein the residue issubjected to cracking temperature under conditions to effect theformation of a high yield of gas oil constituents adapted for conversioninto gasoline, directing the viscosity-broken products into a separateevaporating zone wherein separation of vapors from residue takes place,passing the separated vapors into a separate fractionating zone andsubjecting the vapors therein to fractionation to form a heavy refluxcondensate and a lighter condensate comprising such gas oilconstituents, passing resultant heavy `reflux condensate to a secondaryviscosity-breaking zone wherein the heavy condensate is subjected tocracking temperature under conditions to effect the formation of a highyield of gas oil constituents adapted for conversion into gasoline,separating the latter viscositybroken products into vapors and residueand passing the separated vapors into said separate fractionating zone,passing residual material separated out from the viscosity-brokenproducts from both of said viscosity-breaking zones to a vacuum flashingzone wherein the residual material is subjected to ash distillationunder sub-atmosphericv pressure to form heavy residue and vacnum-flasheddistillate, combining resultant vacnum-flashed distillate constituentswith the heavy reflux condensate passing to the secondaryviscosity-breaking zone, combining said lighter fractions obtained fromthe viscosity-broken products and from the crude petroleum fractionationand subjecting the combined fractions to cracking in a separate crackingzone under high cracking temperature and under conditions of highcracking per pass to effect conversion to gasoline of high anti-knockquality and directing the resultant products of the lattercracking intoa separate fractionating zone to recover the desired gasoline product.

6. In the cracking of hydrocarbon oils the process that comprisessubjecting crude petroleum in a primary fractionating zone tofractionation to form a residue and a lighter fraction, passing saidresidue to a, primary viscosity-breaking zone wherein the residue issubjected to cracking temperature under conditions to eiect theformation of a high yield of gas oil constituents adapted for conversioninto gasoline, directing the viscosity-broken products into a separateevaporating zone wherein separation of vapors from residue takes place,passing the separated vapors into a separate fractionating zone andsubjecting the vapors therein to fractionation to form a heavy refluxcondensate and a lighter condensate comprising such gas oilconstituents, passing resultant heavy reflux condensate to a secondaryviscositybreaking zone wherein the heavy condensate is subjected tocracking temperature under conditions to effect the formation of a highyield of gas oil constituents adapted for conversion into gasoline,directing the latter viscosity-broken products into said separateevaporating zone, withdrawing residue from the latter evaporating zoneand subjecting it to vacuum distillation in a ashing zone held undersub-atmospheric pressure to form heavy residue and vacuum-asheddistillate and introducing resultant vacuumashed distillate into theaforesaid separate fractionating zone so that any portion of thevacuum-flashed distillate remaining unvaporized after contact with thevapors undergoing fractionation therein will be charged to saidsecondary viscosity-breaking zone with said heavy reiiux condensate,combining said lighter fractions obtained from the viscosity-brokenproducts and from the crude petroleum fractionation and subjecting thecombined fractions to cracking in a separate cracking zone under highcracking temperature and under conditions of high cracking per pass toeffect conversion to gasoline of high anti-knock quality and directingthe resultant'products of the latter cracking into a separatefractionating zone to recover the desired gasoline product.

7. In the cracking of hydrocarbon oils the process that comprisessubjecting crude petroleum in a primary fractionating zone tofractionation to form a residue and a lighter fraction,passing saidresidue to a primary viscosity-breaking zone wherein the residue issubjected to cracking temperature under conditions to effect theformation of a high yield of gas oil constituents adapted for conversioninto gasoline, directing the viscosity-broken products into a separateevaporating zone wherein separation of vapors from residue takes place,passing the separated vapors into a separate fractionating zone andsubjecting the vapors therein to fractionation to form a heavy reuxcondensate and a lighter condensate comprising such gas oilconstituents, passing resultant heavy reux condensate to a secondaryviscosity-breaking zone wherein the heavy condensate is subjected tocracking temperature under conditions to effect the formation of a highyield of gas oil constituents adapted for conversion into gasoline,separating the latter viscositybroken products into vapors and residueand passing the separated vapors into said separate fractionating zone,passing residual material separated out from the viscosity-brokenproducts from both of said viscosity-breaking zones to a vacuum flashingzone wherein the residual material is subjected to flash distillationunder subatmospheric pressure to form heavy residue and vacuum-asheddistillate, introducing resultant vacuum-flashed distillate into theaforesaid separate fractionating zone so that any portion of thevacuum-ashed distillate remaining unvaporized after contact with thevapors undergoing fractionation therein will be charged to saidsecondary viscosity-breaking zone with said heavy reflux condensate,combining said lighter fractions obtained from the viscosity-brokenproducts and from the crude petroleum fractionation and subjecting thecombined fractions to cracking in a separate cracking zone under highcracking temperature and under conditions of high cracking per pass toeifect conversion to gasoline of high anti-knock quality and directingthe resultant products of the latter cracking into a separatefractionating zone to recoverthe desired gasoline product.

8. In the cracking of hydrocarbon oils the process that comprisessubjecting crude petroleum in a primary fractionating zone tofractionation to form a residue and a lighter fraction, passing saidresidue to a primary viscositybreaking zone wherein the residue issubjected to cracking temperature under conditions to eect the formationof a high yield of gas oil constituents adapted for conversion intogasoline, directing the viscosity-broken products intoa separateevaporating zone wherein separation of vapors from residue takes place,passing the separated vapors into a separate fractionating zone andsubjecting the vapors therein to fractionation to form a heavy reuxcondensate and a lighter condensate comprising such gas oilconstituents, passing resultant heavy reux condensate to a secondaryviscosity-breaking zone wherein the heavy condensate is subjected tocracking temperature under conditions to effect the formation of a highyield .of gas oil constituents adapted for conversion into gasoline,separating the latter viscosity-broken products into vapors and residueand passing the separated vapors into said separate fractionating zone,passing residual material separated out from the viscosity-brokenproducts from both of said viscosity-breaking zones to a vacuum flashingzone wherein the residual material is subjected to ash distillationunder sub-atmospheric pressure to form heavy residue and vacuumfiasheddistillate, combining resultant vacuumashed distillate constituents withthe heavy reflux condensate passing to the secondary viscosity-breakingzone, combining said lighter fractions obtained from theviscosity-broken products and from the crude petroleum fractionation andsubjecting the combined fractions to cracking in a separate crackingzone under high cracking temperature and under conditions of highcracking per pass to eilg'ect conversion to gasoline of high anti-knockquality, directing the resultant products of the latter cracking intoanother evaporating zone wherein separation of vapors from residue takesplace, passing the-sep arated vapors into a separate fractionating zonewherein the vapors are fractionated to form a reflux condensate and ai'lnal distillate product, passing resultant reflux condensate to afourth cracking zone wherein it is subjected to cracking temperature toeffect conversion into gasoline constituents and directing the resultantproducts of conversion into said latter separating zone.

9. In the cracking of hydrocarbon oils the process that comprisesprimarily subjecting crude petroleum to a stripping operation toseparate it into vapors and residue and fractionating the vapors to forma condensate, passing said residue to a primary viscosity-breaking zonewherein the residue is subjected to cracking temperature underconditions to effect the formation of a high yield of gas oilconstituents adapted for conversion into gasoline, directing theviscositybroken products into a separate evaporating zone whereinseparation of vapors from residue takes place, passing the separatedvapors into a separate ractionating zone and subjecting the vaporstherein to fractionation to form a heavy reflux condensate and a lightercondensate, comprising such gas oil constituents, passing resultantheavy reflux condensate to a secondary viscosit 1- breaking zone whereinthe heavy condensate is subjected to cracking temperature underconditions to eiect the formation of a high yield of gas oilconstituents adapted for conversion into gasoline, directing the latterviscosity-broken products into said separate evaporating zone,withdrawing residue from the latter evaporating zone and subjecting itto vacuum distillation in a ashing zone held under sub-atmosphericpressure to form heavy residue and vacuum-flashed distillate andintroducing resultant vacuumlashed distillate into the aforesaidseparate fractionating Zone so that any portion of the vacnum-flasheddistillate remaining unvaporized after contact with the vaporsundergoing fractionation therein wil be charged to said secondaryviscosity-breaking zone with said heavy reux condensate, combining saiddighter condensate obtained from the viscosity-broken products with saidcondensate obtained from the stripping of the crude petroleum andsubjecting the combined condensates to cracking in a separate crackingzone under high temperature and conditions of high cracking per pass toeiect conversion into gasoline of high anti-knock quality, directing theresultant products of the latter cracking into another evaporating zonewherein separation of vapors from residue takes place, passing theseparated vapors into a separate fractionating zon'e wherein the vaporsare fractionated to form a reflux condensate and a nal distillateproduct, passing resultant reux condensate to a fourth cracking zonewherein it is subjected to cracking temperature to eiect conversion intogasoline constituents and directing the resultant products of conversioninto said latter separating zone.

PERCIVAL C. KEITH, JR. JOSEPH K. ROBERTS.

